1. Field of the Invention
The present invention generally relates to the field of semiconductors. More particularly, the invention relates to fabrication of trench type semiconductor devices.
2. Background Art
In many applications it is desirable for semiconductor devices to provide both high current conduction and high switching speeds. Trench type metal-oxide-semiconductor field-effect transistors (MOSFETs) can achieve high cell density and provide high current conduction. However, trench MOSFETs typically have low switching frequency, partly due to substantial junction capacitances. For example, in conventional trench MOSFETs the entire drain may contribute to feedback capacitance. Thus, conventional trench MOSFETs can exhibit large switching power losses at high frequencies.
Laterally diffused metal-oxide-semiconductor (LDMOS) transistors can have high switching speeds for given voltages, partly due to low junction capacitances. For example, in conventional LDMOS transistors, feedback capacitance is primarily comprised of gate-drain overlap, which is minimal. Thus, LDMOS transistors can be more desirable than trench MOSFETs in high frequency applications. However, LDMOS transistors generally have low cell density and low current conduction compared to trench MOSFETs.
Thus, there is a need in the art for a semiconductor device configured for high cell densities that is capable of providing both high switching speeds and high current conduction.